1. Field of the Invention
The present invention relates to electromechanical loudspeaker motor structures, and, more particularly, to an armored voice coil assembly and methods for making armored voice coil assemblies for use in high power, long excursion loudspeaker applications.
2. Description of Related Art
Recent market emphasis on long excursion, high power dissipation loudspeakers (e.g., low frequency drivers or woofers) has challenged manufacturers to make products which will withstand previously unimaginable levels of abuse. DB drag races and other forms of loudness-level competition have created markets for amplifiers and loudspeakers dissipating several kilowatts (kW) for extended periods of time. Such products have been incorporated in auto sound systems generating acoustic outputs exceeding one hundred seventy decibels (170 dB) before failing.
Loudspeakers have well understood limitations. In particular, high power signals drive a speaker's diaphragm or cone into extreme excursions and can cause the usually pistonic motion of the diaphragm to become mis-aligned when driven by more challenging audio signals. Typical prior art woofers utilize circular baskets supporting frustoconical driver diaphragms having a circular peripheral edge carrying an annular surround or suspension. Customarily, the circular small end of the frustoconical diaphragm supports a substantially cylindrical voice coil former upon which is wound a conductive voice coil having positive and negative terminal ends.
Conventional woofers utilize supportive baskets which closely follow the frustoconical shape of the driver diaphragm and support the motor magnet and the circular diaphragm surround in a co-axial alignment, permitting the axial movement of the diaphragm in response to electrical excitation of the voice coil.
Loudspeaker or woofer failure can be often attributed to thermal or mechanical overloading problems. Substantial amounts of power are required to provide competition-winning sound pressure levels, and signals having such power require very large current flow through voice coil conductors, thus generating substantial amounts of heat and driving the woofer's diaphragm to extreme excursions. Those extreme excursions generate extreme mechanical loads on the diaphragm and its supportive suspension. In competitions, operators seek the loudest possible playback and often over-drive the loudspeaker drivers, causing voice coils to burn out or open circuit. Such extreme use may also cause mechanical failure of the cone, the surround, the “spider” suspension member, or, when a moving, mis-aligned voice coil rubs the motor's annular gap edge, failure of the voice coil.
There is a need, therefore, for a voice coil adapted to withstand the abuse encountered in modern high-power long-excursion loudspeaker applications.
When assembling loudspeakers, one critical alignment step usually adds substantially to the cost and duration of the assembly operation. The loudspeaker motor must be assembled with the substantially cylindrical voice coil located precisely and concentrically in an annular motor gap. The cone and voice coil are usually part of a first assembly that is lowered into a second assembly comprising a motor and basket. If the assembler mis-aligns the voice coil in the annular magnetic gap, the voice coil may contact or rub the magnetic gap's edge, thereby causing distortion or failure of the loudspeaker. The criticality of this alignment increases the cost of assembling loudspeakers.
There is also a need, therefore, for a voice coil assembly adapted to permit a less critical and costly loudspeaker assembly process.